Polls show that roughly one person in two is concerned about manmade global warming. Why? Because vivid, alarming forecasts, even those based on weak foundations, are persuasive. For a while at least.

We’ve seen this many times before. Take the alarm over mercury in fish: in 2004, an Environmental Protection Agency employee warned that 630,000 babies per year were born at risk of brain and nervous system damage due to “unsafe” levels of mercury in their mothers’ blood. Expectant mothers were discouraged from eating fish.

Japan consumes a lot of fish, and the supposedly unsafe levels cited by the EPA are exceeded by 74% of women of childbearing age there. Yet there is no evidence that their children are mentally deficient. In fact, only benefits have been reported from high levels of fish consumption, including good brain function and improved intelligence at age four.

Roughly one person in two is concerned about man-made global warming. Why? Because vivid, alarming forecasts are persuasive only for a time. We've seen it all before. Take the alarm over mercury in fish.

In 2004, a United States Environmental Protection Agency employee warned that each year 630,000 babies were born at risk of brain and nervous system damage due to ''unsafe'' levels of mercury in their mothers' blood.

It turns out that ''at risk'' meant having concentrations of mercury in the blood that were higher than unjustifiably low levels.

The Japanese consume a lot of fish and those ''at risk'' levels are exceeded by 74 per cent of Japanese women of childbearing age and by centuries-old mummified remains.

Yet, there is no evidence that Japanese are mentally deficient, and only benefits have been reported from high levels of fish consumption, including good brain function and improved intelligence at age four.

The validity of the manmade global warming alarm requires the support of scientific forecasts of (1) a substantive long-term rise in global mean temperatures in the absence of regulations, (2) serious net harmful effects due to global warming, and (3) cost-effective regulations that would produce net beneficial effects versus alternatives policies, including doing nothing.

Without scientific forecasts for all three aspects of the alarm, there is no scientific basis to enact regulations. In effect, the warming alarm is like a three-legged stool: each leg needs to be strong. Despite repeated appeals to global warming alarmists, we have been unable to find scientific forecasts for any of the three legs.

We drew upon scientific (evidence-based) forecasting principles to audit the forecasting procedures used to forecast global mean temperatures by the Intergovernmental Panel on Climate Change(IPCC)—leg “1” of the stool. This audit found that the IPCC procedures violated 81% of the 89 relevant forecasting principles.

Our research findings challenge the basic assumptions of the State Department's Fifth U.S. Climate Action Report (CAR 2010). The alarming forecasts of dangerous manmade global warming are not the product of proper scientific evidence-based forecasting methods. Furthermore, there have been no validation studies to support a belief that the forecasting procedures used were nevertheless appropriate for the situation. As a consequence, alarming forecasts of global warming are merely the opinions of some scientists and, for a situation as complicated and poorly understood as global climate, such opinions are unlikely to be as accurate as forecasts that global temperatures will remain much the same as they have been over recent years. Using proper forecasting procedures we predict that the global warming alarm will prove false and that government actions in response to the alarm will be shown to have been harmful.

Whether climate will change over the 21st Century, by how much, in what direction, to what effect, and what if anything people could and should do about any changes are all forecasting problems. Given that policy makers currently do not have access to scientific forecasts for any of these, the policies that have been proposed with the avowed purpose of reducing dangerous manmade global warming—such as are described in CAR 2010 Chapters 4, 5, 6, and 7—are likely to cause serious and unnecessary harm.